Banded knee extensions to isolate and burn the quads.
Squeeze your quad at full extension and resist the band on the way back.
Anchoring a band low behind you and straightening your knee against it isolates the quads the way the machine version does, with tension building toward full extension where the squeeze counts most. There's no seat and no stack, but the principle is identical, pure knee extension with everything else taken out of the movement. It's ideal for finishing off the quads at home, for rehab-style high-rep work, and for feeling the muscle without loading the hips or spine at all.
The machine offers heavier, smoother loading, but the band version isolates the same movement and shines for high reps, home training and pump work. Squeeze hard at lockout and control the return and the quads can't tell the difference at moderate intensities.
Either works, the steps allow both. Seated is more stable and easier to isolate, standing adds a light balance element. Pick whichever lets you keep tension smooth through the whole rep.
You're letting the band win the eccentric. Fight it back to the bent position over two or three seconds, that resisted return is half the exercise.
